Students know the color of light striking an object affects the way the object is seen.. Students know an object is seen when light traveling from the object enters the eye... Students
Trang 1Genre Comprehension Skill Text Features Science Content
Nonfi ction Predict • Captions
• Call Outs
• Diagrams
• Glossary
Light
Scott Foresman Science 3.2
Standards Preview
Standard Set 2 Physical Sciences
2 Light has a source and travels in a
direction As a basis for understanding
this concept:
2.a Students know sunlight can be
blocked to create shadows.
2.b Students know light is reflected
from mirrors and other surfaces.
2.c Students know the color of light
striking an object affects the way the object is seen.
2.d Students know an object is seen
when light traveling from the object enters the eye.
ISBN 0-328-23520-2
ì<(sk$m)=cdfcaj< +^-Ä-U-Ä-U
by Arlene Block
Physical Sciences
Trang 2Genre Comprehension Skill Text Features Science Content
Nonfi ction Predict • Captions
• Call Outs
• Diagrams
• Glossary
Light
Scott Foresman Science 3.2
Standards Preview
Standard Set 2 Physical Sciences
2 Light has a source and travels in a
direction As a basis for understanding
this concept:
2.a. Students know sunlight can be
blocked to create shadows.
2.b. Students know light is reflected
from mirrors and other surfaces.
2.c. Students know the color of light
striking an object affects the way the object is seen.
2.d. Students know an object is seen
when light traveling from the object enters the eye.
ISBN 0-328-23520-2
ì<(sk$m)=cdfcaj< +^-Ä-U-Ä-U
by Arlene Block
Physical Sciences
Trang 3How does light
travel?
The Path of Light
The Sun is the main source of energy for Earth
Energy from the Sun comes to Earth as light Light
is a form of energy Light travels in a straight line
away from its source Light moves outward in all
directions
3
Light and Shadow
Light hits objects that are in its way Opaque
objects can block light They keep it from moving
in the same direction When an object blocks light,
a shadow forms behind it A shadow is an area
that does not receive light directly
Kinds of Shadows
The size of a shadow can change It depends on where the light comes from The Sun is overhead in this picture The shadows are the same size as the tables and chairs When light comes from the side, the shadows will be different
These tables and chairs are opaque They block sunlight and form shadows.
Trang 4What Your Eye Sees
The eye is the part of the body that is sensitive
to light How do you see an object? Light from
a source shines on an object The light from the
object travels to your eye Light passes from the
front of your eye to the back of your eye An
upside-down picture forms there
Your eye sends a message to your brain Your
brain fl ips the picture Then your brain helps you
know what you are seeing
5
What happens when an object, such as a car, blocks what you are seeing, such as a dog? Your eye can no longer see the dog! This is because the car blocks the light coming from the dog Instead, your eye sees the car This shows how light travels
in a straight line
Trang 5What is refl ected
light?
What happens when light hits an object? The
light will refl ect, or bounce off, the object The
refl ected light keeps moving in a straight line The
line goes in a different direction than before the
light hit the object
We can see an object because it refl ects light In
a dark room, no light can refl ect off objects That’s
why you can’t see them
The smooth surface of this lake refl ects light like a mirror.
Refl ection in a Mirror
Some objects have a very smooth surface Light that refl ects from this surface travels in the same direction Objects that refl ect light in this way
are called mirrors A mirror is a surface made of
shiny material We can see objects refl ected in a mirror
Light hits the mirror and is refl ected.
7
Trang 6Refl ection Off Other Surfaces
Some objects have a rough surface What
happens when light refl ects off a rough surface? It
scatters in many directions All you see is the rough
object You don’t see any other objects refl ected in it
This rough paper scatters light from the scissors You cannot see an image on the paper.
Exploring a Refl ected Light Beam
Water mist is sprayed in this dark room Light from a fl ashlight is passing through the mist
Some light hits tiny drops of water in the air This refl ected light moves in all directions Some of
it enters your eyes You can see an image of the beam This shows the path of the light It is moving
in a straight line
A beam of light shines through the water mist.
Some light hits water droplets It is refl ected back
to your eyes.
9
Trang 7What are the colors
of objects?
Different colors of light make up sunlight These
colors combine to form white light What happens
when sunlight strikes an object? Many objects
absorb, or take in, some of the light They refl ect
the rest of the light
The refl ected light determines the color of
the object The color can be red, yellow, or
blue It can also be a mix of these colors
What if no light shines on the object? Then
the object has no color!
11
Colors Your Eyes See
You can see the colors an object refl ects You cannot see the colors an object absorbs A yellow tulip absorbs all colors except yellow Yellow is the color that is refl ected An object that refl ects all colors looks white An object that absorbs all colors looks black
Each of these objects refl ects
a different color.
Trang 8Exploring Sunlight
This fl ower has fi ve cut out parts Each part has
a different colored piece of cellophane on it
Sunlight can pass through each part But only
the color of the cellophane passes through The
other colors are absorbed Some of the colors in
sunlight can be seen this way
Each colored part in this fl ower
lets in light that is the same color
to show through.
Exploring the Effects of Colored Light
What happens when colored light strikes a white object? The white object will refl ect the color that shines on it Shine a red light on white paper The paper will look red Shine a green light on white paper What do you think the paper will look like?
The color of light affects the way an object is seen.
Trang 9These lightbulbs are made of colored glass Each
bulb shines on a different color box They show
how colored light affects an object’s color Why do
the boxes change color?
The yellow box did not absorb all the blue light
Some of the blue light was refl ected What color is
the box?
Blue light shines on a
yellow box.
Red light shines
on a blue box.
15
The red box absorbed most of the green light shining on it There isn’t any green light being refl ected
This blue box did not absorb all the red light
Some of the red light was refl ected The red light mixed with the blue light The box looks light purple
Green light shines on
a red box.
Trang 10absorb to take in something, such as light
color a property of an object determined
by the light that refl ects from the object
eye the part of the body that is sensitive
to light energy
light a form of energy that travels in a
straight line away from its source
mirror a surface made of shiny material
opaque describes materials that block light
refl ect bounce off, as a light wave does
from an object
shadow an area that does not receive light
directly
1 How does light travel?
2 What happens when light hits an object?
3 What determines the color of an object?
made of many different colors Use an encyclopedia or other reference source Get information about the color wheel Write a paragraph explaining what you learned
blue light shines on your shirt What color will your shirt appear to be?